The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [409]
Thrombosed veins feel hard and cord-like, and should be avoided along with tortuous, sclerosed, fibrosed, inflamed or fragile veins, which may be unable to accommodate the device to be used and will result in pain and repeated venepunctures (Dougherty 2008). Use of veins which cross over joints or bony prominences and those with little skin or subcutaneous cover, for example the inner aspect of the wrist, will also subject the patient to more discomfort (Dougherty 2008). Therefore, preference should be given to a vessel that is unused, easily detected by inspection and palpation, patent and healthy. These veins feel soft and bouncy and will refill when depressed (Weinstein and Plumer 2007).
Evidence-based approaches
Rationale
Indications
Venepuncture is carried out for two reasons:
to obtain a blood sample for diagnostic purposes
to monitor levels of blood components.
Methods of improving venous access
There are a number of methods of improving venous access.
Application of a tourniquet: this promotes venous distension. The tourniquet should be tight enough to impede venous return but not restrict arterial flow. The tourniquet should be placed about 7–8 cm above the venepuncture site. It may be more comfortable for the patient to position it over a sleeve or paper towel to prevent pinching the skin. The tourniquet should not be left on for longer than 1 minute as this may result in haemoconcentration or pooling of the blood, leading to inaccurate blood results (Hoeltke 2006).
The patient may be asked to clench the fist and encourage venous distension but should avoid ‘pumping’ as this action may affect certain blood results, for example potassium (Ernst 2005, Garza and Becan-McBride 2010).
Lowering the arm below heart level also increases blood supply to the veins.
Light tapping of the vein may be useful but can be painful and may result in the formation of a haematoma in patients with fragile veins, for example thrombocytopenic patients (Dougherty 2008).
The use of heat in the form of a warm pack or by immersing the arm in a bowl of warm water for 10 minutes helps to encourage venodilation and venous filling (Lenhardt et al. 2002).
Ointment or patches containing small amounts of glyceryl trinitrate have been used to improve local vasodilation to aid venepuncture (Weinstein and Plumer 2007).
Methods for insertion
Asepsis is vital when performing a venepuncture as the skin is breached and a foreign device is introduced into a sterile circulatory system. The two major sources of microbial contamination are:
1 cross-infection from practitioner to patient
2 skin flora of the patient.
Good handwashing and drying techniques are essential on the part of the nurse; gloves should be changed between patients (see Chapter 3).
To remove the risk presented by the patient’s skin flora, firm and prolonged rubbing with an alcohol-based solution, such as chlorhexidine 0.5% in 70% alcohol, is advised (RCN 2010). This cleaning should continue for about 30 seconds, although some authors state a minimum of 1 minute or longer (Weinstein and Plumer 2007). The area that has been cleaned should then be allowed to dry to: (i) facilitate coagulation of the organisms, thus ensuring disinfection, and (ii) prevent a stinging pain on insertion of the needle due to the alcohol on the end of the needle. The skin must not be touched or the vein repalpated prior to venepuncture.
Legal and professional issues
Venepuncture is one of the most commonly performed invasive procedures (Castledine 1996) and is now routinely being undertaken by nurses (Ernst 2005). In order to perform venepuncture safely, the nurse must have basic knowledge of the following.
The relevant anatomy and physiology.
The criteria for choosing both the vein and device to use.
The potential problems which may be encountered, how to prevent them and necessary interventions.
The health and safety/risk management of the procedure, as well as the correct disposal of equipment (RCN 2010).
Certain principles, such as adherence to an aseptic technique, must be